As a rule, USAAF pilots did not keep their own flight logs. Some pilots, presumably with pre-USAAF training, did keep their own flight log, but this is unofficial. What the USAAF did keep, for pilots, bombardiers and navigators, is a monthly Form 5, which listed all flights in a month, date, type flown (but not the serial number), route, and length. To my knowledge, these now only exist on microfilm at the Military Personnel Record Center in St Louis. I do not know how easy it is to get at these through the Internet.
For the 354th FG however, there is a collection of mission schedules held at NARA II in Record Group 18, for each squadron, which I believe is complete through about middle April 1945 (so nothing on Summer 1945, if that is what you really want). I can look up the box references at home if you want that, and you can either go to College Park (NARA II) to copy them, or hire a research contractor to copy them for you. These schedules give the name of the pilot, the aircraft's squadron code, and flight time. No other details. NARA II also has a complete set of the combat reports for the 356th FS (only), and only scattered reports for the other two squadrons. Matches between squadron letter codes and aircraft serial numbers can be found in Steve Blake's history of the 354th FG.

Thanks, I have tried AFHRA already and found some interesting information in the unit history of the 354th FG, but no individual flight information.

Hi Frank,

Thank you for the detailed and helpful information. I will try to contact the Military Personnel Record Center in St. Louis. I am mainly interested in post war flights in June 1945 when the unit was temporarily based at Nürnberg Roth airfield.

From your description, NARA will probably not have related documents, but only combat missions until the end of the war in Europe?